Formation and manipulation of optical soliton pulse in a self- and cross-phase modulated four-level inverted Y-type system

Abstract

We have proposed a theoretical model for controllable optical soliton pulse formation in a magnetic-field-assisted four-level inverted Y-type atomic system. The probability amplitudes of the pertinent levels are used to analyze the contrast between self- and cross-phase modulated probe absorption signals. The absorption profiles obtained from the probability amplitudes and the zeroth-order of the pulse propagation constant in the Taylor series are appropriately congruent. The nonlinear Schrödinger equation derived from the Maxwell–Bloch equation determines the respective bright and dark soliton conditions with positive and negative values of the pulse shape parameter. It is demonstrated that the coupling laser field strengths, laser frequency detunings, and the external magnetic field’s direction are the controlling parameters to produce both bright and dark optical soliton pulses. Alongside, the shape of the optical soliton pulses in self- and cross-phase modulation is influenced by the polarization angle of the probe and coupling fields. It is also found that the variation of coupling field strengths may be used to regulate the group velocity of the soliton probe pulse from superluminal to subluminal modes or vice-versa.